ABSTRACT
In Ghana, information on plants antagonistic to nematodes is
scanty compelling farmers to rely on synthetic chemicals which are effective
but pose an environmental threat. This work aimed to evaluate the effect of
aqueous leaf extracts of Khaya senegalensis, Tectona grandis, Azadirachta
indica, Vernonia amygdalina and Bryophyllum pinnatum plants
for the control of Meloidogyne spp. In evaluating the botanicals, a
laboratory, field and pot experiments were conducted. The first
experiment evaluated the effect of extracts from fresh leaves of K.
senegalensis, T. grandis, A. indica, V. amygdalina and
B. pinnatum on eggs hatchability and nematicidal activity against
second stage juveniles of Meloidogyne spp in the laboratory. Results
show that lower egg hatch and higher juvenile mortality occurred in the
extracts and was concentration dependent. A. indica at 25% gave the
lowest mean egg hatch of 2.33 and highest juvenile mortality of 65.16. The
second experiment was carried out to evaluate the effect of aqueous leaf
extracts of K. senegalensis, T. grandis, A. indica,
V. amygdalina and B. pinnatum applied to soil as drench on
tomato plants. Although the botanicals were effective in the laboratory and pot
experiments, they were moderately effective in the field.. The third experiment
was carried out to evaluate the application of leaf extracts of K.
senegalensis, T. grandis, A. indica, V. amygdalina and
B. pinnatum as mulch and soil admixture on growth and severity of
nematode infection on tomato plants. The results indicated that K.
senegalensis, T. grandis, A. indica, V. amygdalina and
B. pinnatum applied as soil-admixtures were more effective in
controlling Meloidogyne than applied as mulch.
CHAPTER ONE
INTRODUCTION
Tomato (Solanum lycopersicum L.) is one of the most widely
accepted fruits in the world because it is mostly consumed worldwide. It is one
of the most important nutritious vegetable crops grown around the world. Ali et
al., (2012) have reported that, in terms of area cultivated, tomato ranks next
to potato whereas, as a processing crop it ranks first in the world. It belongs
to the family of Solanaceae, including crops such as eggplant, pepper, tobacco
and potato.
Tomato is believed to have originated from tropical central
and South America (Cobley & Steele, 1974). Its cultivars in Africa are
believed to have descended from varieties later introduced from Europe
(Villareal, 1980). Several researchers have shown that it was introduced in Ghana
in the 16th and 17th centuries by the Portuguese and has become the most
popular vegetable crop (Norman 1992 & Nkansah et al., 2003). Amuti, (1971)
stated that most of the local varieties produced in Ghana today evolved from
varieties that were introduced by the Portuguese in the 16th and 17th
centuries.
Several researchers have reported that not all varieties are
successful for cultivation in the country. This observation was made by some
researchers who noted that in the coastal savannah areas of Ghana, varieties
which proved successful for cultivation are the local types, Fireball,
Wosowoso, OK1, OK5, OK7-2, OK7-3, ImprovedZuraungu, Marglobe, Victor and Pusa
Early Dwarf (Sinnadurai, 1967; Amuti, 1971 & Blay, 1978).
Tomato has a good adaptation to a wide range of climatic
conditions, and so is found throughout tropical Africa (De Lannoy, 2001).
According to FAO (2005), Ghana has wide range of areas that are suitable for
tomato production. Production of the crop in Ghana is done by small-scale
farmers who grow it basically for its fresh use. However, with the introduction
of irrigation projects, large scale monoculture has become wide spread,
especially in the Northern and Upper Regions, and around southern Volta region.
Tomato production is also vibrant in Akumadan and the Wenchi Districts. Tomato
is also grown commercially at Derma, Techimantia and Tanoso in the Brong-Ahafo
region. Cooperative farming according to Norman (1992) is concentrated around
Mankessim, Swedru, Nsawam, Amasaman, Sege and Dodowa. Farming methods applied
for tomato cultivation are often based on availability of water. The sources of
water such as rainfall, irrigation, wells and riverbeds determine both the
season of farming and the number of times farming is undertaken within the
year. In addition, post harvest losses are very high in Ghana especially during
the peak harvesting period when there is a glut. Norman (1992) reported that
production and yield of tomato in Ghana is affected by several factors. Pests
and diseases have been found to be a major constraint to production, and these
affect the quality and quantity of the produce. Major pests that attack tomato
include plant parasitic nematodes (Berlinger, 1986).
Tomato is an important crop in Ghana (Norman, 1992). It can
be grown under varied conditions; from green house to the field. It contains
important chemical compounds of medicinal importance (Sahlin, 2004). The ripe
tomato fruit is rich in vitamins and a good sourec of A, B, C and minerals
which areimportant in the human diet (Willcox Catignani & Lazarus, 2003).
About 125 million tonnes of fresh tomatoes were produced in the
world in 2008 (FAO, 2010).
In Ghana, about 12,000 hectares of land are under tomato
cultivation and it is estimated that more than 60,000 farmers grow tomato;
Policy Planning and Monitoring and Evaluation Departmentof the Ministry of Food
and Agriculture(PPMED, 1993). In 1987, tomato contributed about 130,000 metric
tons to the total agricultural productions and about 13 billion cedis in
revenue to the Ghanaian economy (PPMED, 1991). Tomato is one of the major
sources of income to farmers and traders in Ghana. It’s usefulness in fresh or
processed form has played a major role in its rapid and widespread adoption as
an important food commodity in the country (Norman, 1992, Horna, Melinda
Jose., 2006 and Asare-Bediako, Showeminio and Buah&
Ushawu., 2007). The crop is the largest contributor to Gross Domestic Product
(GDP) in the countryGhana Statistical Service (1999). In 2004, tomato alone
contributed 607 metric tons to the total agricultural growth and about US$
56,000 in revenue (SRID, 2005).
F A O in 2005 reported that tomato contributed $437,000 to
the Ghanaian economy from export of 4,368 metric tonnes.
Despite the intensive cultivation and potential of tomato in
the tropics, yield in Ghana is very low compared to other tropical countries.
GIPC (2005) and Danquah and Fulton (2007) reported that yield of tomato in the
country is still low (about 7.5 tonnes/hactare) compare to other tropical
counties like Nigeria at 1,860,600metric tones (FAO, 2010). The global
production area for tomato in 2010 was estimated at 151,699,505 tonnes (FAO,
2010). Production in the United States of America in 2010 was 12,858,700 tonnes
(FAO, 2010), Ghana produced just three tonnes per hactare (SRID, 2010). The low
production of tomato in the tropic and sub-tropical regions has been attributed
to the persistent pest problems and inadequate pest management practices (COPR,
1983). Some of these problems include limited availability of improved planting
material, high cost of labour for land preparation, staking, weeding,
harvesting, storability, and nematode diseases among others. Root-knot
nematodes (Meloidogyne spp) according to De Lannoy (2001) are the major pest of
tomato.
Meloidogyne arenaria, Meloidogyne javanica and Meloidogyne
incognita are reported as the main species which attack tomato Clerk (1974).
Apart from tomato which is highly susceptible other members of the Solanaceae
family like the garden egg, pepper and tobacco when grown on even lightly
infested land, fail to produce any remarkable fruit and on severely affected
soil they are killed totally while still young Clerk (1974).
Hemeng (1981) observed 73 – 100% yield loss in tomato in the
Guinea Savannah Zone of Northern region of Ghana to be caused by root-knot
nematodes.
Even though Farmers use a high percentage of their income to
fight nematodes problems every year, their effort is still not enough to reduce
the losses. Mostfarmers would not use nematicide; rather nematicides are
recommended like carbofuran as control measure against root knot disease, but
expensive and these chemicals are toxic to animals and man and therefore pose
great danger to peasant farmers most of whom are illiterates (MoFA, 1995).
Current efforts and campaign being made by Governments of
various countries including Ghana to improve the standard of living through the production and utilization of vegetable (like tomato), could
only be successful if solutions to the problems of pests including plant
parasitic nematodes are found. MoFA (1995) reported that the use of synthetic
nematicides is considered the most effective practical means of combating the
menace of plant parasitic nematodes in tomato but has some serious constraints.
The assault on the environment through the indiserminate use of synthetic
agro-chemicals (Bell, 2000) and unreliable results from crop rotation systems
(Sikora & Fernandez, 2005) has necessitated the search for sustainable,
effective and environmentally acceptable nematode management options.
The World Health Organization (WHO) reported that 20% of
pesticide use in the world poses danger to human health as well as the
environment (Hurtig et al., 2003). Higher level of pesticide has been found in
people residing closer to agricultural fields (Quandt etal., 2004). It has also
been reported that in late 2010, 15 farmers died from suspected pesticide
poisoning in Upper East region of Ghana (NPAS, 2012).
Currently the Ghanaian public and government have come to
realize that the use of chemical pesticides by vegetable farmers to control
pests and diseases in the country is increasing and if agricultural production
is to be sustainable and safe to humans and the environment, then intensive
farming systems should become less dependent on chemical pesticides (Okorley,
Zinnah & Bampoe., 2002).
With concern about the adverse long-term effects of
pesticides on the environment and human health adequate measures are therefore
required to promote the appropriate management of pests and pesticides. Proper
management will ensure that increased and sustainable agricultural production and farm incomes are achieved; that diseases and insect pest
are managed in a sustainable manner, and that the risks to human health and the
environment associated with pesticide use are kept to an acceptable level.
The use of plant extracts and antagonistic microorganisms as
a component of integrated nematode management is gaining wide acceptance
worldwide. Their environmental safety in an environmentally conscious world
also holds promise for their acceptability and use by resource-poor African
farmers Egunjobi and Onayemi, 1981 Zurren and Khan, 1984; and Adegbite, 2003.
The potential for nematicidal activity of indigenous plants
and their products as an alternative for traditional nematicides has been
studied by several works Prot and Kornprobst, (1983); Haseeb, Siiddiqui and
Alam, (1984), Pracer, Tarjan and Hodgson,(1987); Osmam and Viglierchio, (1988);
Adegbite and Adesiyan (2005); and Hasabo and Noweer (2005).
The use of botanical extracts for controlling pest is
appealing because of the growing problem of environmental pollution caused by
synthetic nematicides. Plant extracts have been found to be effective for the
control of plant parasitic nematodes Siddiqui and Allam (1987), (Hussain,
Kumar, Kahn & Tito, 1984); they are easily degraded, leave no harmful
residues, are cheaper, nontoxic to host plant and humansand availability in
many tropical countriesAmadioha, (2003). Extracts of many plants with
anti-helminthic and antimicrobial properties have been proven effective in
controlling plant parasitic nematodes (Ferris & Zheng, 1998). Such plant
species produce different allele-chemicals which have tremendous nematicidal
potential (Sukul, 1992). Compounds occurring in the plants with nematicidal
activity comprise a wide variety of phytochemicals e.g. polythienyls,
acetylenes, alkaloids, fatty acids and derivatives, phenolics, terpenoids alkaloids, fatty acids and
derivatives, phenolics, terpenoids (Chitwood, 1992).He further stated that use
of phytochemicals in crop production could offer sustainable management option.
Nematicidal phytochemicals are generally safe for the
environment and these compounds include repellents, attractants, hatching
stimulants or inhibitors and nematotoxicants, either constitutive or formed in
response to nematode presence (Chitwood, 2002). Information on plants
antagonistic to nematodes is scanty compelling farmers to rely on synthetic
chemicals which are effective but pose an environmental threat (Osei, Fening,
Gowen & Jama, 2010) this lead to increased interest in developing
pesticides of natural origins during recent years.
The objective of this study was, therefore to evaluate the
use of aqueous leaf extract of some plants in Ghana for the management of
root-knot nematode infection on tomato.
The specific objectives were to evaluate:
The specific objectives were to evaluate:
The effect ofAzadirachta indica, Bryophyllum
pinnatum, Khaya senegalensis, Tectona grandis and Vernonia amygdalina on egg hatchability
and nematicidal activity against juveniles of Meloidogyne spp.
The effect of the aqueous leaf
extract of the five medicinal plants on growth and yield of tomato in the
field.
The application of the five plants Azadirachta
indica, Bryophyllum pinnatum, Khaya senegalensis, Tectona grandis and Vernonia amygdalina extracts as mulch and
soil admixture for the control of root-knot disease and growth of tomato.
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